Electrophotography – Supplemental electrophotographic process – Exposure or charging
Reexamination Certificate
2002-03-13
2004-01-13
Grainger, Quana M. (Department: 2852)
Electrophotography
Supplemental electrophotographic process
Exposure or charging
C399S113000
Reexamination Certificate
active
06678491
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical electric charge removal device used in an image forming process of an electrophotographic system for removing residual electric charges on a photosensitive member using light irradiation, and an image formation apparatus, such as a copier or the like, including the same.
2. Description of the Related Art
As is well known, an image formation apparatus of an electrostatic photographic system forms an image by a process including the steps of charging, exposure, development, transfer and fixing. In the case of a copier, for example, the above steps in more detail are as follows. First, a surface of a photosensitive member (photosensitive drum) is uniformly supplied with electric charges by a charger. The surface of the photosensitive member is exposed, by an optical system, to light which is reflected by an original image, thus forming an electrostatic latent image on the surface. Toner (developer) is electrostatically attached so as to develop the electrostatic latent image, thereby forming a toner image on the photosensitive member. Then, electrostatic charges having an opposite polarity to that of the toner is applied to a transfer member, and thus the toner image is transferred on a recording sheet. The transferred toner image is fixed on the recording sheet by heating and pressurizing. In this manner, an image corresponding to the original image is formed on the recording sheet.
To the above-described basic structure of a copier, many functional elements have been added for the purpose of improving the image quality and the image forming efficiency. One example of such functional elements is an optical electrostatic removal device for removing residual electric charges on the photosensitive member by light irradiation. Exemplary optical electric charge removal devices applicable to the above-described copier of an electrophotographic process include an eraser for erasing a defective latent image in a non-image area on the photosensitive member before the development step, a pre-transfer electric charge removal lamp (PTL) for optically reducing the potential of the photosensitive member before the transfer step, and an electric charge removal lamp (QL) for removing residual charges on the photosensitive member after the surface of the photosensitive member is cleaned.
As an irradiating light source used for such an optical electric charge removal device, a discharge tube such as a fluorescent tube or the like, or an LED array
3
shown in
FIG. 25
is used. The LED array
3
includes a great number of LED chips
2
lined on a substrate
1
. Especially recently, such LED arrays are widely used due to an increasing demand for more compact and more inexpensive products. As shown in
FIG. 26
, the LED array
3
includes the LED chips
2
arranged densely. Due to such a structure, the LED array
3
can irradiate a surface of a photosensitive drum
4
substantially uniformly and at a high luminance. However, such a structure uses a great number of LED chips
2
and thus cannot sufficiently reduce the costs.
For example, Japanese Laid-Open Utility Model Publication No. 55-35584 proposes combining a light bulb used as an irradiating light source and an optical conductor formed of a fluorescent light emitting material so as to provide an optical electric charge removal device for irradiating the surface of a photosensitive drum with light to remove residual charges after the surface is cleaned.
Although not regarding an optical electric charge removal device for removing residual charges, the following publications disclose irradiation devices.
Japanese Laid-Open Patent Publication No. 8-43633 discloses an irradiation device including a light source provided at an end and a column-shaped optical conductor formed of a light-transmissive material. The optical conductor includes a light outgoing surface provided on a side surface extending along a longitudinal direction, and a light scattering section provided on a surface facing the side surface. The light scattering section is formed by machining or surface-roughening.
Japanese Laid-Open Patent Publication No. 10-133026 discloses an irradiation device which includes an optical conductor formed of a rod-shaped light-transmissive material. The optical conductor includes an end for receiving light emitted by an LED as a light source and a light outgoing surface provided on a side surface extending along a longitudinal direction. The optical conductor further includes a sawtooth-like area facing the side surface for reflecting and scattering incident light.
Recently, image formation apparatuses of an electrophotographic system adopt a cartridge system in order to reduce the size of the apparatuses and facilitate maintenance. According to this system, a photosensitive member, a charger, a developing section, a cleaner and other elements used for forming an image are integrated into a unit or a process cartridge which is detachable from a main body.
This cartridge system has the following problems. (1) Such a process cartridge is discarded once toner accommodated therein is used up. Therefore, the light bulb as an irradiating light source is also discarded even though the light bulb is recyclable. (2) Mounting the optical electric charge removal device including the above-described LED array on such a disposable process cartridge is unreasonable in terms of cost, resource and energy savings and environmental protection. (3) Since the main body and the process cartridge are coupled to each other via a connector, the system involves an undesirable possibility of malfunction being caused by defective connection of electric circuits. (4) Use of a plurality of LED chips requires a relatively high power consumption for driving the optical electric charge removal device.
The technology disclosed by Japanese Laid-Open Utility Model Publication No. 55-35584 has the following problems. An electric bulb is used as an irradiating light source. Therefore, the power consumption is relatively high, and an optical conductor formed of a fluorescent light emitting material is required for amplifying the irradiating light. In addition, the irradiating light source and an optical conductor of an optical electric charge removal device, which are secured to the main body of the image formation apparatus, are relatively large and are difficult to accommodate in a process cartridge. Especially where such an optical electric charge removal device is secured to a main body of a tandem-system color image formation apparatus including a plurality of process cartridges arranged in parallel, the optical electric charge removal device is too large to be conveniently attached to the color image formation apparatus. Even when the optical electric charge removal device is reduced in size to be attached to the apparatus, malfunction is likely to occur due to defective connection in a power supply circuit for the irradiating light source, for example, in a connection part between the image formation apparatus and the process cartridge. In addition, after the toner in the process cartridge is used up, the irradiating light source, the optical conductor and the like are discarded even through they are still usable. This is unreasonable in terms of resource and energy savings and environmental protection.
The technologies disclosed by Japanese Laid-Open Patent Publication Nos. 8-43633 and 10-133026 are applied to an optical image reading device (i.e., so-called hand-scanner). According to these technologies, the irradiating light source and the optical conductor are integrated together or provided as close as possible to each other. Since a power source for driving the light source is supplied via a cable or another appropriate element, electricity-related troubles such as defective connection or the like hardly occur. However, when the irradiating light source and the optical conductor are mounted on the cartridge for the purpose of facilitating the periodical maintenance work or o
Fujii Kaori
Ino Toshiaki
Kadowaki Hideaki
Kido Eiichi
Kitagawa Takashi
Conlin David D.
Daley, Jr. William J.
Grainger Quana M.
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